Conventional systems allow for biological materials to be positioned in arrays on surfaces. Material can be placed by mechanically putting materials in specific locations (“spotting”), by building cavities to collect the material (micro-wells), by treating the surface in specific regions, or by combinations of these methods. Most of these techniques do not work well for living cells. Once positioned, samples are almost never removed for further analysis or processing.
Adherent cells are typically analyzed by plating them on a surface then looking for them using a microscope. The locations of the cells are random so that finding the cells can be a time consuming process. To speed this up, robotic systems that utilize machine vision are sometimes used to find the cells within the field of view of the microscope image. In some cases a subset of cells are isolated by the following method: A sacrificial base layer is placed over the plate. Cells are grown on the base layer. A high powered laser is used to cut a circle around the cells of interest, through the sacrificial layer. Cells can be isolated by peeling away the sacrificial layer, or by catapulting the cut material from plate using a high powered laser pulse, carrying the cell with it.
Nonadherent cells can be analyzed quickly using a flow cytometer that rapidly flows a stream of cells past a detector apparatus. Cells of interest can be sorted by a downstream electrostatic system that moves droplets into collection containers. This method will also work for other biological media such as proteins and DNA if they can be attached to small beads. This method does not work well for larger samples (such as multi-celled organisms) and is difficult to multiplex.